I have a 84 CJ7 that I have been rebuilding. I have put a crane cam with new valve springs. While it was running I heard some tapping from the valve cover so I decided to remove it and I discovered that one of my rocker arms had some play in it. I decided that I should remove one of the shims I placed under the rocker arms to remove the play. When I started it up it had a lack of power and fireballs out of the exhaust. I quickly shut it down and now I am going to replace the shims. I think I am going to need new push rods for that cylinder. Is it common to have to have different length push rods. Where should I look to get a custom set of push rods? Or is the play in the rocker arms something I should live with. Not an expert could use some help thanks!